Double-door gating safety protection device for a hydraulic power tong

ABSTRACT

A power tong is disclosed for gripping a pipe, the power tong comprising: a frame with a pair of arcuate portions that define both an axial pipe passage and a throat for receiving a pipe laterally into the axial pipe passage; a hydraulic motor for rotating the pipe; a pair of doors for restricting access to the throat, each door mounted to a respective arcuate portion; a valve housing with an inlet port, an outlet port, a fluid chamber, and a valve member, the outlet port being connected to supply hydraulic fluid to the hydraulic motor; and a pair of valve actuators, each valve actuator responsive to the position of a respective door to operate the valve member to reduce fluid pressure through the outlet port when one or both doors are out of a closed position.

TECHNICAL FIELD

The document relates to oil drilling, well repair, and workover withpower tongs security door guards, especially automatic safety protectiondevices for open type hydraulic power tongs with double doors.

BACKGROUND

Open type power tongs may incorporate safety devices. Currently thereare a variety of safety devices for open type power tongs. An example isChina Patent No. 201320611725.5, entitled “One kind of open typehydraulic power tongs gated security apparatus.” The patent discloses atong with gate valves, shafts, brackets, bracket, pin, safety doors,power tong clamp body, the safety doors connected to the opening of thehydraulic motor hydraulic power tongs; a gating valve, the gating valveconnected to the oil inlet and return port of the hydraulic motor; bothends of the shaft end of the shaft of the joint by a pin hinged safetygate, one end fixedly connected to the door control valve spool ends;both ends of the hose connector at one end through the bracket tongsclamp body, one end is fixed to the bracket; bracket and gated valvebody fastened into one. This protection structure promotes safeoperation of single door hydraulic power tongs. However, this structureis not applicable to the larger openings of double-door hydraulic powertongs. Another example is the Chinese patent No. 200920007413.7,entitled “An opening hydraulic power tong with a safety door automaticprotection device”. The patent discloses a tong with a ram-type two-waydoor or on a secure power tong tongs body change the valve; between themanual valve and the hydraulic motor has a double check valve; securitydoor opening or closing of the control mandrel type two-way valve forthe security structure direction. This structure can be used on thedouble door power tongs but there are several practical problems: 1.because the stop valve is set up between the hand-operated directionvalve and the hydraulic motor and it is a double-pilot operated checkvalve for stopping the oil, the hydraulic system will always buildpressure once the door is not closed. 2. the jack-type two-way valve isprovided on the security door or tongs clamp body, is easy to crash, andit is through the tubing and dual pilot check valve is connected to apipeline, so problems may arise when the pipeline is long. Therefore, anew structure is needed for protection devices applied to double-doorhydraulic power tongs.

SUMMARY

An opening type hydraulic power tong with a two-gate structure for safeoperation of the tong.

A power tong for gripping a pipe, the power tong comprising: a framehaving a pair of arcuate portions that define an axial pipe passage anda side opening for passing a pipe laterally into the axial pipe passage;a pair of doors, each door connected to a respective arcuate portion,the pair of doors having an open position and a closed position, inwhich the pair of doors restrict access to the side opening when in theclosed position; and a part connected to detect the position of the pairof doors and to restrict the operation of the power tong when one orboth of the doors are out of the closed position.

A power tong is disclosed for gripping a pipe, the power tongcomprising: a frame with a pair of arcuate portions that define both anaxial pipe passage and a throat for receiving a pipe laterally into theaxial pipe passage; a hydraulic motor for rotating the pipe; a pair ofdoors for restricting access to the throat, each door mounted to arespective arcuate portion; a valve housing with a fluid chamber, aninlet port, an outlet port, and a valve member, the outlet port beingconnected to supply hydraulic fluid to the hydraulic motor; and a pairof valve actuators, each valve actuator responsive to the position of arespective door to operate the valve member to reduce fluid pressurethrough the outlet port when one or both doors are out of a closedposition.

A power tong for gripping a pipe, the power tong comprising: a framehaving a pair of arcuate portions that define an axial pipe passage anda throat for receiving a pipe laterally into the axial pipe passage; ahydraulic motor mounted on the frame for rotating the pipe; a pair ofdoors, each door mounted to a respective arcuate portion, the pair ofdoors having an open position and a closed position, in which the pairof doors restrict access to the throat when in the closed position; avalve housing with an inlet port, an outlet port, a pair of valvemembers, and a fluid chamber connecting the inlet port and the outletport, the valve housing being connected to supply hydraulic fluid insequence through the inlet port, the fluid chamber, and the outlet port;and a pair of valve actuators, each valve actuator responsive to theposition of a respective door to operate a respective valve member toindependently reduce fluid pressure to the outlet port when therespective door is out of the closed position.

The model provides a double-door gating safety protection device with anopening type hydraulic power tong comprising a gating valve, a push-pullcable system, a bracket, a support, a round pin axle, left and rightdoors, a power tong body and a hydraulic motor. The left and right doorsare installed on the power tong body. There is a gate valve bodycomprising two gate valve members. The advancing of its hydraulic fluidport and hydraulic motor, oil return opening communicate with eachother. There are two push-pull cable systems. One end of each cablesystem is connected to a different door. The other end of each cablesystem is connected to the valve body. There may be a model with twoflexible axles, and one end of which connects and passes through a roundpin axle connected to a door (left or right) and one end of which isconnected to the gate valve. One end of each cable may be connected tothe power tong body via a support while the other end may be fastened toa bracket, the bracket connected to the gate valve body. The beneficialeffects of the model are that the two safe gate devices that open thedoor of opening power tong are simple more, reliable, and emergency doorno. 1 is opened, and push-pull cable flexible axle just drives theoff-load of gate valve, and this improves the opening type hydraulicpressure power tong as it protects the operator's personal safety morereliably.

A hydraulic power tongs opening with double-doors gated securitydevices, including gating valve, push-pull cable shaft, bracket,bracket, pin, left and right security door, power tongs clamp body, ahydraulic motor, left right security door installed at the opening ofthe power tong tongs body, push the cable shaft by a flexible shaft,hose, flexible shaft couplings and hose fittings and is characterized inthat: said valve gating by the gating valve body and two gated valvespool, whose port of the hydraulic motor inlet and oil in the return;the push cable for the two shaft ends of a shaft of its hinged joint atone end by a pin on the right security door at one end fixedly connectedto one of the spool valve gated end; both ends of the shaft at the otherend by a pin joint root is hinged on the left security doors, one endfixedly connected to the control gate valve wherein the other end of thespool section; two ends of the hose push cable shaft joint bracket bythe end of the power tong tongs body, one end fixed to the bracket; thebracket and gated valve body fastened into one.

For existing fields where there are open type power tongs securitytechnology deficiencies, the model provides an opening hydraulic powertongs gated double-door safety device.

The model provides a technical solution: one opening hydraulic powertongs double door gated security devices, including gating valve, pushcable shaft, bracket, bracket, pin, safety doors left and right securitydoor, power tong calipers, hydraulic motors, the left and right securitydoor installed at the opening of the power tong tongs body, push thecable shaft by a flexible shaft, hose, flexible shaft couplings and hosefittings and is characterized in that: said gate valve from the valvebody and two gated valve spool, whose port of the hydraulic motor inletand oil in the return; the push cable for the two shaft ends one of itssoft pin connector end of the shaft through the security door hinged onthe right, one end fixedly connected to one of the spool valve gatedend; both ends of the shaft at the other end by a pin joint root ishinged on the left security doors, one end fixedly connected in gatevalve where the other end of the spool; two ends of the hose push cableconnector shaft end bracket on the power clamp body through one endfixed to the bracket; the bracket and gated valve body integrallyfastened.

When the left and right safety doors are closed at the same time, thetwo shafts of the cable system pull both of the gate valve membersforward causing oil port P and port A of the valve body to be connected.In addition, port A and port C or D on the hydraulic motor are connectedto form a hydraulic circuit allowing the hydraulic system to workproperly

When the left and right safety doors are opened at the same time, thetwo shafts of the cable system push both of the gate valve membersbackward and port P and return port O connect allowing hydraulic fluidto flow back to the hydraulic oil tank, which puts the hydraulic systemin the unloading state. In this state the hydraulic power tongs cannotoperate normally

When one of the left and right door is opened, the respective gate valvemember is pushed backward and the respective port P and respectivereturn port O connect allowing hydraulic fluid to flow back to thehydraulic oil tank, which puts the hydraulic system in the unloadingstate. In this state the hydraulic power tongs cannot operate normally

The model has the beneficial effect of opening the doors of the powertong in a more simple and reliable manner. When a door or both doors arein an open position, the cable system drives the gated valve body intothe unloading state, which restricts operation of the power tong. Thisis a significant improvement as it more reliably protects the operator'ssafety.

In various embodiments, there may be included any one or more of thefollowing features: The valve housing comprises a return port connectedto bypass the hydraulic motor, in which the valve member diverts flow tothe return port when one or both doors are out of the closed position.The valve housing may be a diverter valve. The valve member comprises apair of valve members, with each valve actuator responsive to theposition of a respective door to operate a respective valve member todivert flow to the return port when the respective door is out of theclosed position. The valve members restrict flow to the return port whenboth doors are in the closed position. When one door is out of theclosed position and the other door is in the closed position, the inletport communicates with the outlet port and the return port. When both ofthe pair of doors are out of the closed position, fluid communication iscut off between the inlet port and the outlet port. Each of the firstrestriction surfaces and the second restriction surfaces form cylindersin which the first sealing members and second sealing members,respectively, are shaped to reciprocate. Each valve member forms a spoolvalve. Each valve member forms a gate valve. The valve member comprisesa pair of valve members, with each valve actuator responsive to theposition of a respective door to operate a respective valve member toreduce fluid pressure through the outlet port when the respective dooris out of the closed position. A hydraulic fluid reservoir connected tosupply hydraulic fluid to the inlet port of the valve housing, in whichthe valve housing comprises a return port connecting the hydraulic fluidreservoir to the fluid chamber, and in which the valve members: restrictflow to the return port when both doors are in the closed position; anddivert flow to the return port when one or both of the pair of doors areout of the closed position; and in which: when one door is out of theclosed position and the other door is in the closed position, the pairof valve members split fluid flow to the outlet port and the returnport; and when both of the pair of doors are out of the closed position,the pair of valve members cut off fluid flow to the outlet port. Eachvalve member has a first sealing member and a second sealing member, andthe fluid chamber defines a first zone, a second zone, and a third zone,with the first zone communicating with the inlet port, the second zonecommunicating with the outlet port, and the third zone communicatingwith the return port, in which, for each valve member: the first sealingmember regulates fluid flow between the first zone and the second zone;the second sealing member regulates fluid flow between the first zoneand the third zone; when the respective door is in the closed position,the first sealing member is unseated and the second sealing member isseated; and when the respective door is out of the closed position, thefirst sealing member is seated and the second sealing member isunseated. The fluid chamber comprises a pair of conduits that eachconnect the first zone, the second zone, and the third zone, and eachvalve member is disposed for axial movement within a respective conduit,with each respective conduit forming a first restriction surface forseating the first sealing member, and a second restriction surface forseating the second sealing member. The first restriction surfaces andthe second restriction surfaces form cylinders in which the firstsealing members and second sealing members are shaped to reciprocate.For each valve member the first sealing member and the second sealingmember are coaxial and separated by a stem. Each valve member forms agate valve. Each valve actuator connects by mechanical linkage to arespective door. Each mechanical linkage comprises a push and pull cablesystem, such as a power take off cable. Operating the power tong.Closing the pair of doors; and supplying hydraulic fluid through thevalve housing to the hydraulic motor to grip and rotate a pipe withinthe axial pipe passage.

These and other aspects of the device and method are set out in theclaims, which are incorporated here by reference.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will now be described with reference to the figures, inwhich like reference characters denote like elements, by way of example,and in which:

FIG. 1 is a schematic front view of a power tong;

FIG. 2 is a sectional view A-A of FIG. 1;

FIG. 3 is a schematic view of the valve body when both valve member havebeen pushed backwards (both doors are in the open position);

FIG. 4 is a schematic view of the valve body when one of the valvemembers has been pushed backwards (one of the doors is in the openposition).

DETAILED DESCRIPTION

Immaterial modifications may be made to the embodiments described herewithout departing from what is covered by the claims. In the claims, theword “comprising” is used in its inclusive sense and does not excludeother elements being present. The indefinite articles “a” and “an”before a claim feature do not exclude more than one of the feature beingpresent. Each one of the individual features described here may be usedin one or more embodiments and is not, by virtue only of being describedhere, to be construed as essential to all embodiments as defined by theclaims.

Referring to FIGS. 1, 2, 3 and 4: 1, gate valve; 101, gate control valvebody; 102 and 102′, gated valve spool (member); 2, the carriage; and 3:V, pushing cable shaft; 301, a flexible shaft; 302, hose; 303, shaftjoints; 304, hose fittings; 4, the bracket; 5, pin roll; 6, left safetydoor; 7, the right safety door, 8, power tong body; 9, the hydraulicmotor.

The model is further described below in conjunction with theaccompanying Figures.

Referring to FIGS. 1 and 2, a double-door gated safety device with anopening hydraulic power tong comprising a gating valve 1, push-pullcable systems (shafts) 3 and 3′, bracket 2, cable support 4, pin roll 5,left safety door 6, the right safety door 7, power tong body 8 and thehydraulic motor 9 is shown. Left safety door 6 and the right safety door7 are mounted at the opening of the power tong body 8. The push-pullcable system may include a pair of power take off cables, such as a pairof solid cables each with a coating or sheath on the outside. The powertake off cables may extend from a respective door to the diverter valve,so when the respective door opens the cable pulls the diverter valveopen. Push-pull cable shafts 3 and 3′ comprises a shaft 301, hose 302,flexible shaft connector 303 and hose connector 304 (the part from theconnectors 304 to the valve members 102/102′ forms a valve actuator).Gating valve 1 comprises a gate valve body 101 and gate valve spool 102and 102′ (valve members) composed of the gated valve 1 oil chamber a1,a2 (second zone of fluid chamber) and a communication port A (outletport), oil chamber p1, p2 (first zone of fluid chamber) and port P(inlet port) communicates the oil chamber o1, o2 (third zone of fluidchamber) O (return port) and communication ports, oil and fuel tank Oport communicates gated valve 1 oiling ports P and A are connected tothe hydraulic motor 9 via port C, D; one end of each push-pull cableshaft 3 and 3′ is connected to a respective connector 303; one connector303 is hinged to the left safety door 6 via a pin roll 5 and the otherconnector 303 is hinged to the right safety door 7 via another pin roll5; the other ends of the shafts 3 and 3′ are connected to the gate valvemembers 102 and 102′; a end of each hose connector 304 is connected topower tong body 8 via support 4 and the other end of each hose connector304 is connected to bracket 2; bracket 2 and gated valve body 101 is arefastened together.

When both the left safety door 6 and the right safety door 7 are closed,cable shaft 3 and 3′ and respective flexible shafts 301 pull the gatedvalve spool 102 and 102′ forwards causing the gated valve body 101 oilprogress port P and port A to connect and port A connects to hydraulicmotor 9 via port C or D to form a hydraulic circuit. In that state, thehydraulic system works properly. In FIG. 1 each valve member is disposedin a respective conduit, with left and right piston drums (first andsecond sealing members) separated by a narrow stem, with the right drums(second sealing members) mating or seating with a correspondingrespective cylindrical restriction surfaces or conduits between chambersp1 and o1, and p2 and o2, respectively.

Referring to FIG. 3, when both the left safety door 6 and the rightsafety door 7 are open, the cable shafts 3 and 3′ and respective shafts301 push gated valve spool 102 and 102′ backwards causing gate valvebody 101 return ports P and O to connect, which allows hydraulic fluidto flow to the hydraulic oil tank. In that state, the hydraulic systemis in the unloading state and the hydraulic power tongs cannot operatenormally. In FIG. 3 the left drums mate or seat with correspondingrespective cylindrical restriction surfaces or conduits between chambersa1 and p1 and a2 and p2, respectively.

As shown in FIG. 4, when one either the left safety door 6 or the rightsafety door 7 is in the open position, the respective pushing cableshaft 3 or 3′ and the respective shaft 301 wherein a push gated valvespool 102 or 102′ after the shift in this case motivated gated valvebody 101 ports P, A and back to the oil port O port communicatesdirectly back to the hydraulic oil tank, hydraulic system in theunloading state, hydraulic power tongs cannot operate normally.

In some cases the tong is a back up tong, or used in association with aback up tong. In some cases the frame of the tong is connected to abackup tong. In some cases the doors open and close via a sliding orswinging motion. The valve housing need not have a return port, and mayrestrict or cut off the flow through the outlet port when one or bothdoors are out of the closed position. In such cases a system may beemployed to avoid damage to the hydraulic system, such as the pump, whenthe valve housing closes or cuts off flow in the supply line. Forexample a sensor may be employed to detect increasing back pressureupstream of the valve housing, and in response may shut off thehydraulic pump or shunt hydraulic fluid back to the hydraulic reservoir.In some cases the valve actuators are operated via a hydraulic system,or another suitable system such as a servo system. In some cases theposition of each door is detected by a respective sensor, which isconnected to relay signals to be used to control the valve actuators.The sensor may be a wireless sensor.

Reducing fluid pressure may include decreasing to a non-zero flow, orcutting off the fluid flow entirely. The return port may be connectedvia a circuit back to the reservoir, the circuit being unloaded relativeto the connection between the motor and valve housing, such that fluidflows preferentially through the unloaded circuit back to the reservoir.The valve actuators may be connected to operate together. The cables maybe spring loaded or otherwise tensioned to return to initial positions.The valve member may be a single spool valve. Seating refers to thefunction of restricting or blocking fluid flow. The closed positionincludes a fully closed position. The motor may be mounted to the tongbody or frame. The doors cooperate to block the opening, and may have alatch or lock at the tips to secure the doors in place. The safetydevice may operate other than by shutting off the hydraulic motor. Thesafety device may initiate a warning indicator, such as a light oralarm, or may cause a reduction but not termination in motor action. Thedevice may operate a mechanical linkage to control the motor. The out ofclosed position may include a fully open position.

Translation of Chinese non-provisional patent serial no. 204920850 shownbelow.

A Double-Door Gating Safety Protection Device with an Opening HydraulicPower Tong

A double-door gating safety protection device with an opening hydraulicpower tong covers gating valve, push-and-pull flexible axle, bracket,support, pin roll, left and right safety doors, power tong body andhydraulic motor. The left and right safety doors are installed in theopening of the power tong body; the gating valve consists of gatingvalve body and two gating valve elements, whose oil port is connected tooil inlet and return port of hydraulic motor; there are twopush-and-pull flexible axles, between which one end of the joint of bothends of one axle is hinged to the left or right safety door via the pinroll and the other end is fixedly connected to one end of the gatingvalve element; one end of the joint of both ends is fixed to the powertong body via the support and the other end is fixed on the bracket; thebracket and the gating valve body are fastened together. The beneficialeffect of this utility model is that the double-door safety gatingdevice with an opening power tong is simpler and more reliable. Onceboth safety doors are opened or either safety door is opened, thepush-and-pull flexible axle drives the gating valve for unloading, andthus the safety performance of the opening hydraulic power is tongremarkably improved so as to protect the personal safety of operatorsmore reliably.

This utility model safety protection device involving power tong forpetroleum drilling and well repair, especially, the double-door gatingsafety protection device with an opening hydraulic power tong, belongsto the mechanical safety protection technology for oil field.

Due to the safety needed, the opening hydraulic tong for oil field isrequired to be equipped with safety protection devices. At present, theopening hydraulic tong has been improved for several times and now canprovide multiple forms of safety protection. For example, the patent forutility models named “A gating safety protection device with an openinghydraulic power tong” with the Chinese patent No. 201320611725.5published a gating safety device with an opening hydraulic power tongconsisting of gating valve, flexible axle, bracket, support, safetydoors, power tong body and hydraulic motor, of which the safety doorsare installed in the opening of the power tong body; oil port of gatingvalve is connected to the oil inlet and return port of the hydraulicmotor; one end of the flexible joint of both ends of one flexible axleis hinged to the safety door via the pin roll and the other end isconnected to the end of gating valve element, while one end of theflexible joint of both ends of the other flexible axle is fixed on thepower tong body via the support and the other end is fixed on thebracket; the bracket and the gating valve body are fastened together.The safety protection structure can produce great protective effect forthe single-door opening hydraulic power tong, but not for thedouble-door opening hydraulic power tong with a larger opening. Foranother example, the patent for utility models named “A safety doorautomatic protection device with an opening hydraulic power tong” withthe Chinese patent No. 200920007413.7 punished a safety protectionstructure for which the post-rod two-position three way reversing valveis set upon the safety door or the hydraulic power tong body;double-pilot operated check valve is set up between the hand-operateddirection valve and the hydraulic motor; the opening or closing ofsafety door controls the reversing of the post-rod two-position threeway reversing valve. The structure can be used for double door, butshows the following problems in actual utilization: 1. the stop valve isset up between the hand-operated direction valve and the hydraulic motorand it is a double-pilot operated check valve to stop the oil, so thehydraulic system will always build the pressure once the door is notclosed; 2. the post-rod two-position three way reversing valve is set upon the safety door or the hydraulic power tong, causing that it iseasily damaged, and it is connected to the double-pilot operated checkvalve via the oil pipe, so problems may be caused due to too long pipe.Therefore, a new structure is needed for the double-door safetyprotection device with an opening hydraulic power tong for oil fieldpipe.

The utility model provides a double-door gating safety protection devicewith an opening hydraulic power tong regarding the deficiencies in thesafety protection technology of opening hydraulic power tong for oilfield pipes.

The technical proposal of the utility model is a double-door gatingsafety protection device with an opening hydraulic power tong consistingof gating valve, push-and-pull flexible axle, bracket, support, pinaxle, left safety door, right safety door, power tong body and hydraulicmotor. The left and right safety doors are installed in the opening ofthe power tong body and the said push-and-pull flexible axle is composedof flexible axle, flexible pipe, flexible axle joint and flexible pipejoint and is featured with that the said gating valve is composed ofgating valve body and two gating valve elements, with the oil portconnected to the oil inlet and the return port of the hydraulic motor;there are two push-and-pull flexible axles, between which one end of theflexible axle joint of both ends of one flexible axle is hinged to theright safety door via the pin roll and the other end is firmly connectedto the end of one gating valve element; one end of the flexible axlejoint of both ends of the other flexible axle is connected to the leftsafety door via the pin roll and the other end is firmly connected tothe end of the other gating valve element; one end of flexible axlejoint of both ends of two push-and-pull flexible axles is fixed to thehydraulic power tong via the support and the other end is fixed on thebracket; the said bracket and gating valve body are fastened together.

When left and right safety doors are closed at the same time, theflexible axles in two push-and-pull flexible axles pull elements of twogating valves forward, then oil inlet P and oil inlet A are connected inthe gating valve body and oil port A and oil port C or D on thehydraulic motor are connected, and thus an oil hydraulic circuit isformed and the hydraulic system operates normally; when the left andright safety doors are opened at the same time, flexible axles in twopush-and-pull flexible axles pull elements of two gating valvesbackward, then oil inlet P and return port O in the gating valve bodyare connected and hydraulic oil flows back to the oil tank directly sothat the hydraulic system is under the unloading condition, thusresulting in abnormal operation of the hydraulic power tong; when eitherthe left safety door or the right safety door is opened, the openedsafety door drives the flexible axle in the push-and-pull axle to movethe gating valve element backward, and then oil inlet P, oil inlet A andreturn port O are all connected and hydraulic oil directly flows back tothe oil tank so that the hydraulic system is under the unloadingcondition, thus resulting in abnormal operation of the hydraulic powertong.

The beneficial effect of this utility model is that the safety gatingdevice with an opening power tong is simpler and more reliable. Once thesafety doors are opened or either safety door is opened, thepush-and-pull flexible axle will drive the gating valve for unloading,and thus the safety performance of the opening hydraulic power tong canbe improved remarkably so as to protect the personal safety of operatorsmore reliably.

1. A double-door gating safety protection device with an openinghydraulic power tong covers a gating valve, push-and-pull flexible axle,bracket, support, pin roll, left safety door, right safety door, powertong body and hydraulic motor. The left and right safety doors areinstalled in the opening of the hydraulic power tong body and the saidpush-and-pull flexible axle consists of flexible axle, flexible pipe,flexible axle joint and flexible pipe joint with the following features:

The said gating valve is composed of gating valve body and two gatingvalve elements, with the oil port connected to the oil inlet and thereturn port of the hydraulic motor;

Regarding the gating valve, inner oil chamber a1 and inner oil chambera2 are connected to oil port A, oil chamber p1 and oil chamber p2 areconnected to oil port P, and oil chamber o1 and oil chamber o2 areconnected to oil port O.

There are two push-and-pull flexible axles, between which one end of theflexible axle joint of both ends of one flexible axle is connected tothe right safety door via the pin roll and the other end is firmlyconnected to the end of a valve element of gating valve; one end of theflexible axle joint of both ends of the other flexible axle is connectedto the left safety door via the pin roll and the other end is firmlyconnected to the end of the other valve element of the gating valve; oneend of flexible axle joint of both ends of two push-and-pull flexibleaxles is fixed to the hydraulic power tong via the support and the otherend is fixed on the bracket;

The said bracket and gating valve body are fastened together.

FIG. 1 is the front structure diagram of the utility model;

FIG. 2 is the A-A section of FIG. 1;

FIG. 3 is the diagram of two gating valve elements which move backward;

FIG. 4 is the diagram of any gating valve element which moves backward.

Among FIGS. 1, 2, 3 and 4: 1. gating valve; 101. gating valve body; 102and 102′. element of gating valve; 2. bracket; 3 and 3′. push-and-pullflexible axle; 301. flexible axle; 302. flexible pipe; 303. flexibleaxle joint; 304. flexible pipe joint; 4. support; 5. Pin roll; 6. leftsafety door; 7. right safety door; 8. power tong body; 9. hydraulicmotor

Specific Mode of Execution

Here are the further descriptions of the utility model in combinationwith the drawings and examples.

As shown in FIGS. 1 and 2, a double-door gating safety protection devicewith an opening hydraulic power tong consists of gating valve 1,push-and-pull flexible axles 3 and 3′, bracket 2, support 4, pin roll 5,left safety door 6, right safety door 7, power tong body 8 and hydraulicmotor 9. Left safety door 6 and right safety door 7 are installed in theopening of the power tong body 8; push-and-pull flexible axle 3 and 3′is composed of flexible axle 301, flexible pipe 302, flexible axle joint303 and flexible pipe joint 304; the gating valve 1 is composed of thegating valve body 101 and gating valve elements 102 and 102′, in whichoil chamber a1 and a2 are connected to oil port A, oil chamber p1 and p2are connected to oil port, oil chamber o1 and o2 are connected to oilport O, oil port O is connected to the oil tank, and oil port P and oilport A in the gating valve are connected to oil inlet C and return portD in the hydraulic motor; one end of flexible axle joint 303 on bothends of push-and-pull flexible axles 3 and 3′ is hinged to left safetydoor 6 and right safety door 7 via pin roll 5, while the other end isfirmly connected to the ends of gating valve elements 102 and 102′; oneend of flexible pipe joint 304 of both ends is fixed to power tong 8,while the other end is fixed to bracket 2; bracket 2 and gating valvebody 101 are fastened together.

When left safety door 6 and right safety door 7 are both closed,flexible axle 301 in push-and-pull axles 3 and 3′ pulls gating valveelements 102 and 102′ forward, then oil inlet P in gating valve body 101is connected to oil port A and oil port A is connected to oil port C orD in hydraulic motor 9, thus a hydraulic circuit is formed so that thehydraulic system can normally operate.

As shown in FIG. 3, when left safety door 6 and right safety door 7 areboth opened, flexible axle 301 in push-and-pull axles 3 and 3′ pullsgating valve elements 102 and 102′ backward, then oil inlet P in gatingvalve body 101 is connected to oil port O and hydraulic oil directlyflows back to the oil tank, thus the hydraulic system is under theunloading state, resulting in abnormal operation of the hydraulic powertong.

As shown in FIG. 4, when either safety door 6 or right safety door 7 isopened, one of flexible axle 301 in push-and-pull axles 3 and 3′ pullsgating valve elements 102 and 102′ backward, then oil inlet P, oil portA and oil port O are connected in gating valve body and hydraulic oildirectly flows back to the oil tank, thus the hydraulic system is underthe unloading state, resulting in abnormal operation of the hydraulicpower tong.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A power tong forgripping a pipe, the power tong comprising: a frame with a pair ofarcuate portions that define both an axial pipe passage and a throat forreceiving a pipe laterally into the axial pipe passage; a hydraulicmotor for rotating the pipe; a pair of doors for restricting access tothe throat, each door mounted to a respective arcuate portion; a valvehousing with a fluid chamber, an inlet port, an outlet port, and a valvemember, the outlet port being connected to supply hydraulic fluid to thehydraulic motor; and a pair of valve actuators, each valve actuatorresponsive to the position of a respective door to operate the valvemember to reduce fluid pressure through the outlet port when one or bothdoors are out of a closed position.
 2. The power tong of claim 1 inwhich the valve housing comprises a return port connected to bypass thehydraulic motor, in which the valve member diverts flow to the returnport when one or both doors are out of the closed position.
 3. The powertong of claim 2 in which the valve member comprises a pair of valvemembers, with each valve actuator responsive to the position of arespective door to operate a respective valve member to divert flow tothe return port when the respective door is out of the closed position.4. The power tong of claim 3 in which the valve members restrict flow tothe return port when both doors are in the closed position.
 5. The powertong of claim 4 in which: when one door is out of the closed positionand the other door is in the closed position, the inlet portcommunicates with the outlet port and the return port; and when both ofthe pair of doors are out of the closed position, fluid communication iscut off between the inlet port and the outlet port.
 6. The power tong ofclaim 3 in which each valve member has a first sealing member and asecond sealing member, and the fluid chamber defines a first zone, asecond zone, and a third zone, with the first zone communicating withthe inlet port, the second zone communicating with the outlet port, andthe third zone communicating with the return port, in which, for eachvalve member: the first sealing member regulates fluid flow between thefirst zone and the second zone; the second sealing member regulatesfluid flow between the first zone and the third zone; when therespective door is in the closed position, the first sealing member isunseated and the second sealing member is seated; and when therespective door is out of the closed position, the first sealing memberis seated and the second sealing member is unseated.
 7. The power tongof claim 6 in which the fluid chamber comprises a pair of conduits thateach connect the first zone, the second zone, and the third zone, andeach valve member is disposed for axial movement within a respectiveconduit, with each respective conduit forming a first restrictionsurface for seating the first sealing member, and a second restrictionsurface for seating the second sealing member.
 8. The power tong ofclaim 7 in which each of the first restriction surfaces and the secondrestriction surfaces form cylinders in which the first sealing membersand second sealing members, respectively, are shaped to reciprocate. 9.The power tong of claim 7 in which each valve member forms a spoolvalve.
 10. The power tong of claim 3 in which each valve member forms agate valve.
 11. The power tong of claim 1 in which the valve membercomprises a pair of valve members, with each valve actuator responsiveto the position of a respective door to operate a respective valvemember to reduce fluid pressure through the outlet port when therespective door is out of the closed position.
 12. The power tong ofclaim 1 in which each valve actuator connects by mechanical linkage to arespective door.
 13. The power tong of claim 12 in which each mechanicallinkage comprises a push and pull cable system.
 14. A method ofoperating the power tong of claim
 1. 15. The method of claim 14 furthercomprising: closing the pair of doors; and supplying hydraulic fluidthrough the valve housing to the hydraulic motor to grip and rotate apipe within the axial pipe passage.